As cities become more crowded, there’s less room for open public spaces. There are more cars, with less space for parking. And with storms intensifying due to climate change, cities have to think about what to do when existing infrastructure can’t handle the deluge, and these are only a few of the challenges facing cities in the coming years.

But a new concept from the Danish architecture and urban design firm Third Nature offers a single answer to all three problems. Called Pop-Up, the concept proposes an underground reservoir for water overflow with a parking structure that literally floats on top of it. On sunny days, the parking structure is entirely submerged below the ground–and the space on top can be used as a public park. But on rainy days, the parking structure rises up out of the ground as the reservoir fills up with water.

That might sound far-fetched, but the firm worked with the structural engineering firm Cowi and consultancy Ramboll to ensure the feasibility of the concept. The idea is based on Archimedes’ principle of floatation: the buoyancy of the parking structure is designed so that it has the same density as the displaced water. A system of mechanical lifts ensures that the parking garage stays balanced as it adjusts based on how much water is in the reservoir.

“Cities are in extreme situations where billions need to be spent on climate mitigation solutions and the equivalent amount on handling densification of the cities, especially the conflict between cars and urban spaces, so for us it is natural to think of the solutions together,” says Flemming Rafn Thomsen, a partner at Third Nature, in a statement. “It is a serious game with the infrastructural systems that provide real viability and completely new types of experiences back to the city’s users.”

Third Nature also makes a business case for the concept. Even though the idea would cost three times as much as simply building a parking structure above ground, the consulting firm Ramboll estimates that the project would be profitable if a five-story structure were priced at $325 per square foot, or if a seven-story structure were priced at $250 per square foot. The structure would also play triple duty as a public park and as an emergency reservoir.While Pop-Up remains a concept, it presents a fascinating portrayal of the city as a multitiered entity, with different levels that change and adjust over time. This kind of thinking–if not this concept itself–could ultimately make urban areas more resilient to the shocks and stresses of climate change.

ABOUT THE AUTHOR Katharine Schwab is a contributing writer at Co.Design based in New York who covers technology, design, and culture. More